(1) Field of the Invention
This invention relates to marine towing apparatus and more particularly to a fluid bearing for towed array bends.
(2) Brief Description of the Prior Art
It is known in the art that sonar capabilities of submarines or surface ships can be provided or enhanced by means of towed arrays of electrical or optical cables having acoustical sensors disposed along their length and at their terminal ends. Such arrays can be deployed by assemblies for paying out the cable and for subsequently reeling in and storing the cable. Such a system is described, for example, in U.S. Pat. No. 5,263,431.
Referring to FIG. 1, another somewhat different conventional apparatus for deploying or retrieving a towed array is shown. It will be seen that a towed array 10 passes through a number of bends 12 which in the art are frequently referred to as "roller boxes". This conventional apparatus also includes a winch 14 which includes capstan drive 16, capstan idler 18 and capstan drive motor 20. Adjacent the winch 14, there is a storage drum 22 and storage drum motor 24.
During retrieval, the capstan drive 16 rotates to reel in the array 10 to the capstan idler 18 and then back to the capstan drive 16, usually for a plurality of turns. During deployment, the array 10 is reeled into the storage drum 22. After a plurality of turns around the capstan idler 18, the cable is urged around the bend 12. It then passes through guide tube 30 to the aft of the submarine or other vehicle. It will thus be understood that the array 10 extends in an oblique first length from the storage drum 22 to the winch 14 and to the bend 12. At the bend 12, the direction of the array is changed and it extends rearwardly in a longitudinal second length 30. The array 10 extends to where its direction is changed again in additional bends 36 and 38 before extending through the hull of the submarine at exit 44 to deployed array 46.
Referring to FIG. 2, there is shown a prior art roller box type of bend 12. It will be seen that this roller box includes an inner guide 48 wherein a number of rollers such as roller 50 are transversely mounted. Inner guide 48 is mounted by brackets 54. The array 10 is directed through and retained within a guide tube 26. The rollers 50 are positioned on the inside of each bend in contact with array 10 to reduce friction that would normally occur between the array and the inside bend radius of the guide tube 26 when the array is being retrieved. By means of this arrangement, the desired degree of bend may be introduced into the cable 10. The use of the rollers, however, such as roller 50 introduces point loading on the array, with high stresses and associated fatigue damage inflicting upon the array components. This is due primarily to the rollers inability to completely support the array from "flattening".
A need, therefore, exists for a means for changing the direction of a towed array cable which does not introduce such point loads and consequently avoids such high stresses and associated reduce reliability.